Na+ 135-145 meg/L
- H2O – 60% male, 50% female
- TBW – 1/3 ECF (1/4 IV, ¾ IS) , 2/3 ICF
- 85-90% of total body Na+ is extracellular (95% K+ is intracellular)
ECF Volume
- Depletion: deficit in total body Na+ (renal or extrarenal loss > Na intake)
- Expansion: salt intake with renal Na+ retention (renal disorder or 2O to decrease effective circulating volume – HF or hypoalbumin)
Hyponatremia
- Isotonic → hyperlipidemia, hyperprotenemia; no change in osmolarity; ↓ H2O volume so that ↓[Na] in plasma volume (pseudo!)
- Hypertonic → hyperglycemia; ↑ glucose draws H2O into EC space from cells
- Hypotonic → assess volume status (clinically)
- Hypovolemic:
- Extrarenal salt loss (GI)
- Renal salt loss (diuretics, ACEi, mineralocorticoid deficiency, etc.)
- Euvolemic:
- SIADH (↓Na, ↓urea, ↓plasma osmolarity, ↑urine osmolarity)
- Psychogenic polydipsia
- Asymptomatic
- H2O restric
- 0.9% NS and furosemid
- Demeclocycline – inhibit AD
- Symptomatic
- Saline 3% and furosemid
- Watch out for central pontine myelinolysis if corrected too fast (1-2 meq/L/h
- Hypervolemic: edema associated disease
- Treatment – H2O restrict and diuretics
- Hypovolemic:
Hypernatremia
- Concentrated urine (urine osmolarity > 400 mosm/kg)
-
- renal H2O conserving function norma
- Non-renal loss (sweat, respiratory, stool)
- Renal loss (osmotic diuresis – glycosuria, mannitol, urea
-
- Dilute urine (urine osmolarity < 250 mosm/kg)
- Central DI
- Renal insensitivity to ADH
- Nephrogenic (Li or demeclocycline) DI
- Relief of urinary tract obstruction
- Nephritis